Neuropathic pain is the result of a malfunction somewhere in the nervous system. The site of the nervous system injury or malfunction can be either in the peripheral or central nervous system. Neuropathic pain is often triggered by disease or injury and is frequently described as having a burning, lancinating, or electric shock characteristic. Persistent allodynia—pain resulting from a non-painful stimulus, such as light touch—is also a common characteristic of neuropathic pain. Neuropathic pain is frequently chronic.
Chronic neuropathic pain is often caused by one or more nerves being compressed or entrapped. Nerve compression may result from direct external pressure or contusion related to trauma, work, hobbies, or sports activities. Additionally or alternatively, nerve compression may be caused by structural abnormalities within the body. The exact mechanism of nerve compression is not completely understood and may include varying degrees of friction and ischemia.
Clinical manifestations of nerve compression include pain, which may be sharp or burning, and paresthesia. In more severe cases, there may be weakness distal to the site of compression. Physical symptoms of nerve compression include muscle atrophy, weakness, and involuntary twitching of muscle fibers. A person's reflexes may also be affected, depending on the site of the compression. Pain associated with nerve compression is often intensified during sleep.
Nerve compression syndromes can affect many different parts of the body. For example, commonly affected locations in the upper extremity include the thoracic outlet, shoulder girdle, elbow, forearm, wrist, and thumb. Lower extremity nerve compression syndromes commonly occur in the pelvis and around the knee, ankle, and foot.
One of the more common nerve compression syndromes is carpal tunnel syndrome (CTS), which affects millions of Americans and results in billions of dollars of workers compensation claims every year. In CTS, the median nerve is compressed at the wrist and often results in tingling, numbness, sleep disruption, coldness, weakness, and/or pain. Most cases of CTS are idiopathic. While repetitive activities are often blamed for the development of CTS, the correlation is often unclear. Physiology and family history may also play a role in an individual's susceptibility to CTS.
Various treatment therapies have been used to treat or curtail the occurrence of CTS and other nerve compression syndromes. For example, immobilizing braces, massages, ultrasonic therapy, localized steroid injections, and anti-inflammatory drugs such as ibuprofen or aspirin have all been used with varying levels of success. Severe cases of nerve compression can sometimes be remedied through surgical procedures. For example, CTS may be alleviated through a surgical procedure in which the transverse carpal ligament is cut to relieve pressure from the compressed median nerve. However, each of these treatment therapies can be ineffective, offer only temporary relief, or cause other undesirable side effects.